Log consumed record in a file

[mrebiai]

When Kapoeira consumes records, we could maybe also store them into a file for more external assertions.

A first syntax

Then expected records and log to file output.log
      | topic_alias| key        | value  |
      | topic-out  | my-key | result1 |
      | topic-out  | my-key | result2 |

And output.log could be

output1
output2